Microelectronic components generate heat in use and can be damaged if they exceed acceptable operating temperatures. As high-energy microelectronic components become more prevalent and powerful, the thermal load produced by these components becomes increasingly difficult to dissipate from the system.
Microelectronic components are commonly attached to a substrate such as a printed circuit board (PCB) to form a larger microelectronic component assembly. A single microelectronic component assembly will often have numerous microelectronic components, each of which generates heat in use, mounted on a single PCB. Dissipation of heat from the side of the PCB bearing the microelectronic components has been and continues to be a significant problem for PCB designers.
A variety of approaches are used in the art to dissipate heat generated by microelectronic components. One solution employs surface-mounted thermal risers with prongs or fins to dissipate heat to the air adjacent the PCB. Other approaches use arrays of copper plated holes (vias) that conduct the thermal load through the PCB and thence to a thermal mass, e.g., a chassis or housing for the microelectronic component assembly or a secondary heat sink on the back side of the finished assembly. One of the most effective thermal management devices is the use of a metal coin or slug to conduct the thermal load through the circuit board to such a thermal mass. After the PCB is formed, e.g., by laminating multiple layers together, a through-opening or cavity may be machined through the thickness of the PCB, forming a passage between the component side and the back side of the PCB. Coins or slugs are then mounted in the opening or cavity using thermal grease or solder, typically as part of the component assembly process during which microelectronic components are mounted on the PCB.
The following patents, the entirety of each of which is incorporated herein by reference, generally relate to PCB thermal management features:
U.S. Pat. No. 5,779,134—Method for surface mounting a heat sink to a printed circuit board
U.S. Pat. No. 6,411,516—Copper slug pedestal for a printed circuit board
U.S. Pat. No. 6,190,941—Method of fabricating a circuit arrangement with thermal vias
U.S. Pat. No. 6,200,407—Method of making a multilayer circuit board having a window exposing an enhanced conductive layer for use as an insulated mounting area.